In order to form printed images from electric image signals such as computer outputs or facsimile signals by utilizing an electronic photocopying process, it is necessary to convert said electric image signals into optical signals.
As means for obtaining the aforementioned optical signals for the electrostatic recording apparatus, there have been provided a means using a laser such as that disclosed in U.S. Pat. No. 3,750,189 and a means using a light emission diode (LED) array such as that disclosed in U.S. Pat. No. 4,342,504. However, when the laser is used, the recording apparatus should include relatively large-sized, complicated and expensive mechanisms such as a laser oscillator and a polygonal mirror and requires a highly accurate optical system, whereby it has heretofore been difficult to provide a small-sized and inexpensive printer. In the case of the LED array, in turn, a plurality of short LED array tips are arranged in a line since it is difficult to form the dense LED to have the length of, e.g., A4 size. The arrangement of the LED array tips requires high accuracy, and utilization of a plurality of the LED arrays results in complexity of the driving circuits for the LED arrays.